<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style media="screen">
    *{
      padding:0;
      margin:0;
    }
    #hd{
      width: 80%;
      height: 600px;
      border: 3px solid blue;
      margin: 0 auto;
      display: flex;
    }
    #hd div{
      width: 300px;
      height: 300px;
      background: orange;
      border: 1px solid green;
      font-size: 50px;
      color: whte;
      line-height: 300px;
      text-align: center;
      color:white;
    }
  </style>
</head>
<body>

  <!-- order属性可以定义元素的排列位置 -->
  <!-- 默认是0，值越小位置越靠前 -->
  <div id="hd">
    <div>1</div>
    <div>2</div>
    <div style="order:1;">3</div>
    <div>4</div>
    <div>5</div>
    <div>6</div>
    <div>7</div>
  </div>


</body>
</html>
